What is the difference between proportional control and on/off control?
On/off control opens or closes the valve fully; movement starts abruptly and stops abruptly. In proportional control the amount of joystick movement is converted into speed, and the load is positioned precisely without being shaken.
On/off control knows only two states: open or closed. Movement starts at full speed and stops suddenly when released. It is sufficient in simple applications, but the load swings.
In proportional control, how far you push the joystick determines the speed of the movement. It gives a smooth start and stop; the difference is clear in loader, bucket and crane applications that require precise positioning.
The full topic: Converting a tractor hydraulic lever to electronic control